Effects of Acute Beetroot Juice Ingestion and Hypoxic Conditions on Metabolic Function, Skeletal Muscle Oxygenation, and Cardiac Function During Endurance Exercise in Healthy Young Men.
BRJ supplementation may help attenuate hypoxia-induced skeletal muscle deoxygenation, as reflected in Deoxy_Hb, potentially via NO-mediated mechanisms, though findings should be regarded as preliminary evidence for the potential use of BRJ as a nutritional strategy in hypoxic exercise settings.
Key Findings
Results
Hypoxic conditions required a significantly lower mechanical load compared to normoxic conditions during submaximal exercise fixed at 70% HRmax.
Twelve healthy adult males completed four conditions in a randomized, crossover, double-blind design.
Exercise was performed for 30 minutes at 70% HRmax under normoxic (FiO2 20.9%) or hypoxic (FiO2 14.5%) conditions.
The lower mechanical load in hypoxia indicates that the same relative heart rate intensity required less external work output, reflecting greater physiological stress.
A two-way repeated-measures ANOVA was used to test main effects of environment, treatment, and their interaction.
Results
A significant environment × treatment interaction was observed for deoxygenated hemoglobin (Deoxy_Hb), with HBRJ statistically indistinguishable from normoxic conditions.
This interaction indicates that BRJ specifically attenuated the hypoxia-induced increase in skeletal muscle oxygen extraction.
The HBRJ condition did not differ significantly from either normoxic condition (NPLA or NBRJ) in Deoxy_Hb.
The hypoxic placebo condition (HPLA) showed greater oxygen extraction compared to normoxic conditions, while HBRJ did not.
This was described as a 'clear attenuation of the hypoxia-induced increase in oxygen extraction.'
Skeletal muscle oxygenation was measured using near-infrared spectroscopy (NIRS) reflecting Deoxy_Hb.
Results
A significant main effect of treatment was observed for respiratory exchange ratio (RER), without a significant environment × treatment interaction.
BRJ supplementation produced a significant main effect on RER regardless of oxygen environment.
HBRJ did not differ significantly from NBRJ in RER, suggesting BRJ influenced substrate metabolism similarly across conditions.
No significant interaction effect for RER was found, indicating the treatment effect was consistent across normoxic and hypoxic environments.
RER reflects the ratio of carbon dioxide produced to oxygen consumed and is used as an indicator of metabolic substrate utilization.
Methods
BRJ supplementation of 70 mL containing 400 mg nitrate (NO3-) was ingested 2.5 hours before exercise.
The BRJ dose was 70 mL providing 400 mg NO3-.
Participants ingested BRJ or placebo 2.5 hours prior to 30 minutes of submaximal exercise.
This timing was chosen to allow sufficient time for dietary nitrate to be converted to nitric oxide via the enterosalivary nitrate-nitrite-NO pathway.
Circulating nitrate/nitrite concentrations were not directly measured in this study, which is noted as a limitation.
Results
Hypoxic conditions induced greater physiological stress than normoxic conditions across multiple measured outcomes.
The hypoxic fraction of inspired oxygen was FiO2 14.5%, approximating altitude-equivalent hypoxic stress.
Greater physiological stress under hypoxia was reflected in the need for reduced mechanical load to maintain the same heart rate target.
The study design used a fixed heart rate intensity (70% HRmax) to standardize cardiovascular demand across environments.
Significant main effects of environment were observed, consistent with known hypoxia-induced physiological responses.
Results
Most outcome variables did not show a significant environment × treatment interaction, limiting conclusions about BRJ's effects across multiple physiological domains.
Significant interaction effects were confirmed only for Deoxy_Hb.
No significant interaction was found for cardiac function variables or most metabolic variables.
The authors state that 'interaction effects were not confirmed for most variables.'
Findings are described as 'preliminary evidence' given these limitations and the absence of direct nitrate/nitrite biomarker measurements.
The study included only 12 participants, which may limit statistical power to detect interaction effects.
What This Means
This research suggests that drinking beetroot juice before exercise in low-oxygen (hypoxic) environments — similar to high-altitude conditions — may help maintain better oxygen delivery to working muscles. In this small study, 12 healthy young men exercised at a fixed moderate intensity under both normal and low-oxygen conditions, with and without beetroot juice. The key finding was that when participants drank beetroot juice before exercising in hypoxic conditions, the amount of oxygen extracted from the blood by their muscles looked similar to what was seen during exercise in normal air, rather than the elevated extraction typical of hypoxia. This suggests beetroot juice may partially compensate for the reduced oxygen availability at altitude or in low-oxygen settings.
Beetroot juice is rich in inorganic nitrate, which the body converts into nitric oxide — a molecule that helps dilate blood vessels and improve blood flow. The researchers propose this mechanism may explain why beetroot juice appeared to reduce the extra physiological strain caused by exercising with less oxygen. Additionally, beetroot juice influenced how the body used fuel during exercise (reflected in the respiratory exchange ratio), though this effect was similar in both normal and low-oxygen conditions.
This research suggests beetroot juice could be a useful nutritional strategy for people exercising in hypoxic environments, such as mountain climbers, high-altitude athletes, or workers in low-oxygen settings. However, the authors caution that these are preliminary findings from a small sample, that blood nitrate levels were not directly measured to confirm the proposed mechanism, and that most other physiological measures did not show a clear benefit specific to hypoxic conditions. Larger studies are needed to confirm these results.
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Choi J, Lee E, Park H, Jung W, Woo S, Kim S, et al.. (2026). Effects of Acute Beetroot Juice Ingestion and Hypoxic Conditions on Metabolic Function, Skeletal Muscle Oxygenation, and Cardiac Function During Endurance Exercise in Healthy Young Men.. Nutrients. https://doi.org/10.3390/nu18172780